Biology subjects

Bugeon, J.

Publications and source records attributed to Bugeon, J..

10 recordsLinked to original sources

bioRxiv2026

Declining muscle hyperplasia in juvenile trout is driven by rapid limitation of muscle stem cell capacity and niche functionality

Unlike mammals and birds, where new muscle fiber formation (hyperplasia) ceases around birth, large and fast-growing fish such as rainbow trout undergo a spectacular post-hatching surge of hyperplasia, followed by a considerably delayed hyperplasia decline. This study investigated the roles of the satellite cells (SCs) and their niche in this decline by determining the number and the myogenic capacity of the muscle progenitors as well as the functionality of their direct tissue environment. Histological analysis revealed a significant decrease in hyperplasia (fibers <25 {micro}m) and SC numbers (Pax7+) between 10 g and 500 g trout. Transplantation experiments using muscle-derived cells (MDCs) from mlc2-GFP transgenic trout (10 g to 2 kg donors into 10 g to 2 kg recipients) demonstrated a marked decline in both intrinsic myogenic capacity and niche functionality as trout grow from 10 g to 500 g. Detailed analyses of GFP+ fibers produced after transplantation showed an enrichment of small-diameter GFP+ fibers in 10 g but not 100 g trout recipient muscles, showing a rapid impairment in niche ability to support hyperplasia. In addition, transplantation of MDCs from trout of different ages but the same weight, showed that increasing trout weight, but not aging, is associated with an impairment of the myogenic capacity of progenitors and their niche. Overall, these findings show that the muscle hyperplasia decline in trout is primarily driven by early impairment of the SC niche, followed by a reduction in their myogenic capacity and number, with weight gain playing a more critical role than aging.

cell biology↗

bioRxiv2024

Mature adipocytes inhibit differentiation of myogenic cells but stimulate proliferation of fibro-adipogenic precursors derived from trout muscle in vitro.

Interactions between tissues and cell types, mediated by cytokines or direct cell-cell exchanges, regulate growth. To determine whether mature adipocytes influence the in vitro development of trout mononucleated muscle cells, we developed an indirect coculture system, and showed that adipocytes (5x106 cells/well) derived from perivisceral adipose tissue increased the proliferation (BrdU+) of the mononucleated muscle cells (26% versus 39%; P<0.001) while inhibiting myogenic differentiation (myosin+) (25% versus 15%; P<0.001). Similar effects were obtained with subcutaneous adipose tissue-derived adipocytes, although requiring more adipocytes (3x107 cells/well versus 5x106 cells/well). Conditioned media recapitulated these effects, stimulating proliferation (31% versus 39%; p<0.001) and inhibiting myogenic differentiation (32% versus 23%; p<0.001). Adipocytes began to reduce differentiation after 24 hours, whereas proliferation stimulation was observed after 48 hours. While adipocytes did not change pax7+ and myoD1/2+ percentages, they reduced myogenin+ cells showing inhibition from early differentiation stage. Finally, adipocytes increased BrdU+ cells in the Pdgfr+ population but not in the myoD+ one. Collectively, our results demonstrate that trout adipocytes promote fibro-adipocyte precursor proliferation while inhibiting myogenic cells differentiation in vitro, suggesting the key role of adipose tissue in regulating fish muscle growth.

cell biology↗

bioRxiv2023

From the third to the seventh generation of selection for muscle fat content in rainbow trout: Consequences for flesh quality

Muscle lipid content was shown to affect many quality features in salmonids in both raw and processed fillets. The objective of the present work was to assess the consequences of 7 generations of divergent selection for muscle adiposity on some rainbow trout flesh quality and muscle parameters. Fish from Lean (L) and Fat (F) lines had a similar body weight but L fish were longer and had consequently lower condition factor values. Carcass yield was not affected by selective breeding, but L fish had lower hepato- and gonado-somatic indexes, a bigger head, and lower fillet yield than F fish. A difference of more than 15 points in mean fat-meter(R) values (genetic selection criteria) was measured between the two lines. Mean muscle lipid content was 5.0{+/-}1.0% for L line vs 13.5{+/-}2.2% for F line. An absolute difference of more than 6% was measured in fillet dry matter content between the two lines, for raw, cooked, and smoked fillets. Raw fillets from F fish were lighter (L*>) and more colorful (a* and b*>), but softer than those from the L line. Quality parameters of cooked fillets were very similar between the two lines, whereas smoked fillets exhibited, between the two lines, similar differences than raw fillets. A large difference in white muscle fiber size was observed, fish from F line having higher fiber mean diameter, a lower proportion of small fibers, and a higher proportion of large fibers. Sex effects were observed on these immature fish, on classically sex-related traits (GSI and head development), but also on muscle fiber size. Moreover, these effects were more marked in F line. Correlation analysis showed that raw fillet color was positively related to muscle adiposity whereas mechanical resistance was negatively related. Raw fillet mechanical resistance was also negatively correlated to white muscle fiber size. Moreover, smoked fillet quality parameters were correlated to raw fillet ones. The relationships between muscle adiposity, but also muscle cellularity, and fillet quality were discussed. HighlightsO_LI7 generations of adiposity divergent selection affect raw and smoked fillet quality. C_LIO_LISelective breeding led to a noteworthy response in white muscle cellularity. C_LIO_LISome differences between male and female was measured in immature pan-size trout. C_LI Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=195 SRC="FIGDIR/small/569019v1_ufig1.gif" ALT="Figure 1"> View larger version (37K): org.highwire.dtl.DTLVardef@10b25f6org.highwire.dtl.DTLVardef@e9402aorg.highwire.dtl.DTLVardef@173b1f9org.highwire.dtl.DTLVardef@a9898b_HPS_FORMAT_FIGEXP M_FIG C_FIG

physiology↗

bioRxiv2023

Looking for a needle in a haystack: de novo phenotypic target identification reveals Hippo pathway-mediated miR-202 regulation of egg production

Understanding microRNA (miRNA) functions has been hampered by major difficulties in identifying their biological target(s). Currently, the main limitation is the lack of a suitable strategy to identify biologically relevant targets among a high number of putative targets. Here we provide a proof of concept of successful de novo (i.e., without prior knowledge of its identity) miRNA phenotypic target (i.e., target whose de-repression contributes to the phenotypic outcomes) identification from RNA-seq data. Using the medaka mir-202 knock-out (KO) model in which inactivation leads to a major organism-level reproductive phenotype, including reduced egg production, we introduced novel criteria including limited fold-change in KO and low interindividual variability in gene expression to reduce the list of 2,853 putative targets to a short list of 5. We selected tead3b, a member of the evolutionarily-conserved Hippo pathway, known to regulate ovarian functions, due to its remarkably strong and evolutionarily conserved binding affinity for miR-202-5p. Deleting the miR-202-5p binding site in the 3 UTR of tead3b, but not of other Hippo pathway members sav1 and vgll4b, triggered a reduced egg production phenotype. This is one of the few successful examples of de novo functional assignment of a miRNA phenotypic target in vivo in vertebrates.

genomics↗

bioRxiv2023

Gut physiology of rainbow trout (Oncorhynchus mykiss) is influenced more by 1 short-term fasting followed by refeeding than by feeding fishmeal-free diets

Supplementing a fishmeal-free diet with yeast extract improves rainbow trout (Oncorhynchus mykiss) growth performance and modulates the hepatic and intestinal transcriptomic response. These effects are often observed in the long term, but are not well documented after short periods of fasting. Fasting for a few days is a common practice in fish farming, especially before handling the fish, such as for short sorting, tank transfers and vaccinations. In the present study, rainbow trout were subjected to a four-day fast and then refed, for eight days, a conventional diet containing fishmeal (control diet) or alternative diets composed of terrestrial animal by-products supplemented or not with a yeast extract. During the refeeding period alone, most of the parameters considered did not differ significantly in response to the different feeds. Only the expression of claudin-15 was upregulated in fish fed the yeast-supplemented diet compared to the control diet. Conversely, fasting followed by refeeding significantly influenced most of the parameters analyzed. In the proximal intestine, the surface area of villi significantly increased and the density of goblet cell tended to decrease during refeeding. Although no distinct plasma immune response or major signs of gut inflammation were observed, some genes involved in the structure, complement pathway, antiviral functions, coagulation and endoplasmic reticulum stress response of the liver and intestine were significantly regulated by refeeding after fasting. These results indicate that short-term fasting, as commonly practiced in fish farming, significantly alters the physiology of the liver and intestine regardless of the composition of the diet.

physiology↗

bioRxiv2020

VisEgg: A robust phenotyping tool to assess rainbow trout egg features and viability

Assessing female fish reproductive success requires a thorough evaluation of egg characteristics, including egg number, size and variability as well as egg developmental potential through the monitoring of embryo survival after fertilization. While embryonic success relies, at least in part, on paternal contribution, some parameters are strictly related to egg characteristics, one of the main ones being the viability of the egg when released into the water at spawning. It is however not necessarily possible, at least in salmonid fish that lay non-transparent eggs, to separate the different causes of egg/embryo failure. In this context, our aim was i) to develop a simple and rapid system to capture images of rainbow trout eggs combined with computerized processing of these images to perform a fully automatic individual characterization of egg features including number and size ii) to estimate unfertilized egg viability through the monitoring of the percentage of eggs that will not survive to water hydration. To evaluate the VisEgg system, unfertilized eggs (approximatively 400 eggs per batch) originating from 105 different females were hydrated in water. After 24h, a picture of the eggs was obtained using a dedicated shooting system consisting of a light source and a digital single-lens reflex (SLR) camera. An image processing algorithm was developed to allow the automatic detection and separation of the eggs and to perform automatic measurements of egg number and individual egg size. The presence of white egg was used as an indirect measure of egg integrity, the "whitening" being the result of water entry into the egg through the vitelline membrane. These white eggs were therefore considered as non-viable, as a result of their lack of physical integrity. Fertilization assays were performed in parallel using a subsample of the same egg batch. Embryonic development was monitored and hatching rate was calculated. A significant correlation between white egg percentage after hydration and hatching rate was observed (Spearman coefficient =-0.557, p<0.001), in consistency with the fact that non-viable egg will not allow successful embryonic development. In contrast, the percentage of eggs that do not successfully hatched includes egg/embryo failures of different nature including egg viability, their capacity to be fertilized and to develop into an embryo. Using VisEgg, we were able to quantify the lack of viability of the eggs separately from the different other events that may occur during fertilization and incubation. VisEgg is a convenient and reliable tool to obtain individuals measures on trout eggs. It can be used to assess not only egg size and egg number but also unfertilized egg viability before fertilization.

developmental biology↗

bioRxiv2020

C-Eci: A Cubic-Eci Combined Clearing Method For 3D Follicular Content Analysis In The Fish Ovary

Deciphering mechanisms of oocyte development in female fishes still remains challenging and a comprehensive overview of this process at the level of the organ is still needed. The recent development optical tissue clearing methods have tremendously boosted the 3D imaging of large size biological samples that are naturally opaque. However, no attempt of clearing on fish ovary that accumulates extremely high concentration of lipids within oocytes has been reported to date. To face with this ovarian-specific challenge, we combined two existing clearing methods, the non-toxic solvent-based Eci method for efficient clearing and the CUBIC method to enhance lipid removal and reduce non-specific staining. The methyl green fluorescent dye was used to stain nuclei and delineate follicles. Using this procedure (named C-Eci), ovaries of both medaka and trout could be imaged in 3D and all follicles analyzed. To our knowledge this is the first procedure elaborated for clearing and imaging fish ovary in 3D. The C-Eci methods thus provides an interesting tool for getting precise quantitative data on follicular content in fish ovary and promises to be useful for further morphological studies. SummaryA modified ethyl-cinnamate-based clearing method allows solving fish ovary-specific challenges for 3D imaging, including high lipid-contents, and analyzing the ovarian follicular content in medaka and trout.

developmental biology↗

bioRxiv2018

Histological, transcriptomic and in vitro analysis reveal an intrinsic activated state of myogenic precursors in hyperplasic muscle of trout

BackgroundThe dramatic increase in myotomal muscle mass in post-hatching fish is related to their ability to lastingly produce new muscle fibres, a process termed hyperplasia. The molecular and cellular mechanisms underlying fish muscle hyperplasia largely remain unknown. In this study, we aimed to characterize intrinsic properties of myogenic cells originating from fish hyperplasic muscle. For this purpose, we compared in situ proliferation, in vitro cell behavior and transcriptomic profile of myogenic precursors originating from hyperplasic muscle of juvenile trout (JT) and from non-hyperplasic muscle of fasted juvenile trout (FJT) and adult trout (AT).\n\nResultsFor the first time, we showed that myogenic precursors proliferate in hyperplasic muscle from JT as shown by in vivo BrdU labeling. This proliferative rate was very low in AT and FJT muscle. Transcriptiomic analysis revealed that myogenic cells from FJT and AT displayed close expression profiles with only 64 differentially expressed genes (BH corrected p-val < 0.001). In contrast, 2623 differentially expressed genes were found between myogenic cells from JT and from both FJT and AT. Functional categories related to translation, mitochondrial activity, cell cycle, and myogenic differentiation were inferred from genes up regulated in JT compared to AT and FJT myogenic cells. Conversely, Notch signaling pathway, that signs cell quiescence, was inferred from genes down regulated in JT compared to FJT and AT. In line with our transcriptomic data, in vitro JT myogenic precursors displayed higher proliferation and differentiation capacities than FJT and AT myogenic precursors.\n\nConclusionsThe transcriptomic analysis and examination of cell behavior converge to support the view that myogenic cells extracted from hyperplastic muscle of juvenile trout are intrinsically more potent to form myofibres than myogenic cells extracted from non-hyperplasic muscle. The generation of gene expression profiles in myogenic cell extracted from muscle of juvenile trout may yield insights into the molecular and cellular mechanisms controlling hyperplasia and provides a useful list of potential molecular markers of hyperplasia.

cell biology↗

bioRxiv2018

Naa15 knockdown enhances c2c12 myoblast fusion and induces defects in zebrafish myotome morphogenesis

The comprehension of muscle tissue formation and regeneration is essential to develop therapeutic approaches against muscle diseases or loss in muscle mass and strength during ageing or cancer. One of the critical steps in muscle formation is the fusion of muscle cells to form or regenerate muscle fibres. To identify new genes controlling myoblast fusion, we undertook an siRNA screen in c2c12 myoblasts and found that N-alpha-acetyltransferase 15 (Naa15) knockdown enhanced c2c12 myoblast fusion suggesting that Naa15 negatively regulated myogenic cell fusion. We identified two Naa15 orthologous genes in zebrafish genome: naa15a and naa15b. These two orthologs are both expressed in myogenic domain of the somite. Knockdown of zebrafish naa15a and naa15b genes induced a \"U\" shaped segmentation of the myotome and alteration of myotome boundaries resulting in the formation of abnormally long myofibres spanning adjacent somites. Taken together these results show that Naa15 regulates myotome formation and myogenesis in fish.

cell biology↗

bioRxiv2018

MicroRNA-202 (miR-202) controls female fecundity by regulating medaka oogenesis

Female gamete production relies on coordinated molecular and cellular processes that occur in the ovary throughout oogenesis. In fish, as in other vertebrates, these processes have been extensively studied both in terms of endocrine/paracrine regulation and protein expression and activity. The role of small non-coding RNAs in the regulation of animal reproduction remains however largely unknown and poorly investigated, despite a growing interest for the importance of miRNAs in a wide variety of biological processes. Here, we analyzed the role of miR-202, a miRNA predominantly expressed in male and female gonads in several vertebrate species. We studied its expression in the medaka ovary and generated a mutant line (using CRISPR/Cas9 genome engineering) to determine its importance for reproductive success with special interest for egg production. Our results show that miR-202-5p is the biologically active form of the miRNA and that it is expressed in granulosa cells and in the unfertilized egg. The knock out (KO) of miR-202 resulted in a strong phenotype both in terms of number and quality of eggs produced. Mutant females exhibited either no egg production or produced a drastically reduced number of eggs that could not be fertilized, ultimately leading to no reproductive success. We quantified the size distribution of the oocytes in the ovary of KO females and performed a genome-wide transcriptomic analysis approach to identified dysregulated molecular pathways. Together, cellular and molecular analyses indicate that lack of miR-202 impairs the early steps of oogenesis/folliculogenesis and decreases the number of large (i.e. vitellogenic) follicles, ultimately leading to dramatically reduced female fecundity. This study sheds new light on the regulatory mechanisms that control the early steps of follicular development and provides the first in vivo functional evidence that an ovarian-predominant microRNA may have a major role in female reproduction.\n\nAuthor summaryThe role of small non-coding RNAs in the regulation of animal reproduction remains poorly investigated, despite a growing interest for the importance of miRNAs in a wide variety of biological processes. Here, we analyzed the role of miR-202, a miRNA predominantly expressed in gonads in vertebrate. We studied its expression in the medaka ovary and knocked out the miR-202 genes to study its importance for reproductive success. We showed that the lack of miR-202 results in the sterility of both females and males. In particular, it lead to a drastic reduction of both the number and the quality of eggs produced by females. Mutant females exhibited either no egg production or produced a drastically reduced number of eggs that could not be fertilized, ultimately leading to no reproductive success. Quantitative histological and molecular analyses indicated that miR-202 KO impairs oocyte development and is also associated with the dysregulation of many genes that are critical for reproduction. This study sheds new light on the regulatory mechanisms that control oogenesis and provides the first in vivo functional evidence that an ovarian-predominant microRNA may have a major role in female reproduction.

genetics↗